There are many applications today where it is desired to sense position of a moveable object, for example, the angular orientation of a device or apparatus that rotates about a shaft or pivot, or the position of a device that moves in translation. In the prior art, position has often been measured or detected using optical, magnetic or mechanical resolvers or encoders. For example, an optically detectable pattern is provided around or along the periphery of the device where the pattern varies with the position. This pattern is optically detected and decoded to obtain the rotation angle or translational position. Another prior art approach is to use magnetic rings or moveable magnets to produce a magnetic field that varies with the position or angular rotation of the object to which they are attached. While the optical and moveable magnet approaches have the advantage of being non-contact measuring arrangements they may suffer one or more number of disadvantages, including undesirable complexity and/or inadequate resolution for many applications.
Still further prior art approaches utilize variable potentiometers or capacitors whose wiper arms or plates move with the rotation or translation of the moveable object so that the resistance or capacitance measured across the variable device gives an indication of the position of the object. While the variable potentiometer and capacitor approach are inexpensive, they may suffer from the disadvantage that they may need to be mechanically coupled to the object whose angular orientation or translational location is being measured. A further potential disadvantage of the variable potentiometer approach is that potentiometers may be less reliable as compared to other sensor types. In applications where very high reliability is desired, e.g., space applications, this potentially lower reliability is undesirable. Accordingly there continues to be a need for position measuring devices, such as angle and translation measuring devices, that are reliable, economical, and of adequate resolution.
Accordingly, it is desirable to provide an improved position measuring device and method, especially for measuring the angular position of a shaft or a device rotating about a shaft or pivot, or for measuring the location of a translating device or object, or both. In addition, it is desirable that the sensing apparatus and method be simple, rugged, and reliable and not require any brushes or wiper arms or similar moving mechanical coupling to the device or object whose orientation or position is being sensed. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.